A voluntary drug test showed Alvarez had trace amounts of the drug in his system and Golden Boy Promotions said in a statement on Monday the level was "consistent with meat contamination that has impacted dozens of athletes in Mexico over the last years."

"These values are all within the range of what is expected from meat contamination," Golden Boy quoted Daniel Eichner, director of the WADA-accredited SMRTL lab that conducted the tests, as saying.

The promotion company headed by Mexican ring great Oscar de la Hoya said it had notified the Nevada State Athletic Commission and Golovkin's promoter Tom Loeffler.

"We're waiting to get a ruling from the Nevada commission," Loeffler told AFP.

"Whenever you have a positive test, it's never a good thing. But we'll wait until we get the information. As of now, nothing has changed from our side. Gennady is still training and hoping that the fight continues, but we'll leave it up to the commission."

Undefeated Golovkin and Alvarez fought to a split draw in a September 16 thriller that ended amid some controversy.

While one judge scored the fight for Golovkin and one had it even, there was widespread astonishment at the card of judge Adalaide Byrd, who marked it 118-110 in favor of Alvarez.

"This is a fight that Gennady has wanted," Loeffler said. "He was begging Canelo for the first fight and naturally wanted the second fight after the controversy with the judges in the first.

"He's certainly not looking to get out of this fight for any reason. But at the same time, there's a reason why testing is in place. But we just have to wait for the results and see how that shakes out."

Golden Boy said Alvarez will immediately move his training camp from Mexico to the United States "and will submit to any number and variety of additional tests" deemed necessary in the build up to the May bout.

Alvarez said the positive result "surprises and bothers me".

"I will submit to all the tests that require me to clarify this embarrassing situation and I trust that at the end the truth will prevail," he said.

Tainted meat has been blamed before for positive clenbuterol tests in Mexico, where it is sometimes used to fatten cattle.

The World Anti-Doping Agency warned athletes at the 2011 Pan American Games in Guadalajara to be careful about what they ate during the event.

FIFA, world football's governing body, concluded that contaminated meat resulted in positive tests of 109 players at the Under-17 World Cup in Mexico that year, when five members of Mexico's national team also tested positive.